Mechanism of Incomplete Mitral Leaflet Coaptation—Interaction of Chordal Restraint and Changes in Mitral Leaflet Coaptation Geometry: Insight from In Vitro Validation of the Premise of Force Equilibrium

Figures

Graphical representation of the left ventricle in a long-axis projection. The impact of papillary muscle (PM) displacement on mitral leaflet coaptation geometry and chordal insertion geometry is schematized (A), and supported by force diagrams for the closed mitral valve condition with normal papillary muscle alignment (B) and following papillary muscle displacement (C). For the closed mitral valve in equilibrium in systole, the pressure forces (FΔP) resulting from the transmitral pressure acting to close the leaflets (coapting forces) are counterbalanced by tethering forces from the annular (FA) and papillary muscle attachments. These force components have different origin and direction, however, their projections along the individual chordae as the chordal coapting (FC) and chordal tethering forces (FT) are also in equilibrium. This force balance of the individual chordae is based on a counterbalance between the coapting forces projected along the chordae (FC) and the projected tethering forces (FT) from the papillary muscle and annular attachment. Since the transmitral pressure force, FΔP, acts perpendicular to the surface area of the anterior and posterior leaflet, the magnitude of the (projected) chordal coapting force component depends on the transmitral pressure difference, the surface area of the anterior and posterior mitral leaflets and the chordal insertion angle (θ) onto the mitral leaflets (see text for details).

The chordal force measure of each chordae tendineae consisted of the chordal tethering force component (FT) and the chordal coapting force component (FC). The difference of the force components, (FC−FT), defined the resulting (valvular directed) force of the chordae tendinea acting on the leaflets at the point of insertion.

Diagram of a midsystolic tented mitral leaflet geometry (left) with a typical leaflet contour imaged by 2D echo from apical view (right). Left ventricular side in z-direction. The occlusional leaflet areas of the anterior and posterior leaflet (AAL and APL) were calculated as the sum of fractions of a cone produced from four apical scanning planes rotated around an axis through the mid point of the annulus (right; one fraction of a cone is marked). Notice leaflet edge separation due to leaflet asynergy creating a regurgitant orifice. Variables to describe leaflet configuration are illustrated (r and h). The intersection of the anterior leaflet extension on the posterior leaflet gives the horizontal length r4 and perpendicular distance h4 of the posterior leaflet involved in mitral orifice occlusion. αAL and αPL: Systolic leaflet coaptation angle of the anterior and posterior leaflet.

Schematic representation of the three-dimensional reconstruction of the mitral leaflet geometry, using one short axis view of the annulus plane and two parasternal long axis views at the midpoint of the half mitral coaptation line. The primary chordae connected the tip the papillary muscles and the corresponding midpoint of the half mitral coaptation line (* ). The central papillary muscle lines (LAPM and LPPM) are illustrated as double arrows from the papillary muscle tips through the chordae attachment (* ) to the annular plane.

Linear correlations were demonstrated between the orthogonal projections of the chordal coapting force components to the leaflets, ∑([FC,i sin θi]AL and ∑([FC,i sin θi]PL (dependent variables) and the anterior and posterior leaflet occlusional leaflet areas, AAL and APL. Data represents one valve at all test conditions. Trends are representative of all valves (see text).

Free body diagram of the force equilibrium of the anterior mitral valve leaflet, showing the force components acting on the anterior mitral leaflet and along the chordae tendineae. In equilibrium the chordal tethering force (FT) is counterbalanced by the chordal coapting force component (FC). The moment due to the force FΔP applied by ΔP on the leaflet is balanced by the moment due to −FC, which is equal to FT. The papillary muscle is deviating into the plane (x-direction). α, leaflet coaptation angle in the plane of chordal insertion; ϕ, angle of incidence of the chordae with respect to the annular plane. θ, chordal insertion angle with the leaflet (=α+ϕ);LAL, length of the anterior leaflet. AAL, occlusional leaflet area of the anterior leaflet. P0, the centerpoint of the moment of the annular hinge (τA,int=0).

Return to: Mechanism of Incomplete Mitral Leaflet Coaptation—Interaction of Chordal Restraint and Changes in Mitral Leaflet Coaptation Geometry: Insight from In Vitro Validation of the Premise of Force Equilibrium

Copyright in the material you requested is held by the American Society of Mechanical Engineers (unless otherwise noted). This email ability is provided as a courtesy, and by using it you agree that you are requesting the material solely for personal, non-commercial use, and that it is subject to the American Society of Mechanical Engineers' Terms of Use. The information provided in order to email this topic will not be used to send unsolicited email, nor will it be furnished to third parties. Please refer to the American Society of Mechanical Engineers' Privacy Policy for further information.

Shibboleth is an access management service that provides single sign-on protected resources.
It replaces the multiple user names and passwords necessary to access subscription-based content with a single user name and password that can be entered once per session.
It operates independently of a user's location or IP address.
If your institution uses Shibboleth authentication, please contact your site administrator to receive your user name and password.